My computer keeps rebooting!! PLease, somebody help!!

The instalation went well. I'm not overclocking it. The thing is, my computer keeps rebooting randomnly, and it has been over a week. I have done a couple of things to try to find the cause of it:

1- updated BIOS.
2- ran memtest86 twice, each time 12-hour test. There was no error.
3- ran microsoft standar and extended memory diagnostic. Also, no error found.
4- reseated memory to different slots and run test again, not one error.
5- reformatted hard disk and re-installed windows xp sp2.
6- disabled not used onboard features like second LAN controller, 1394 controller.
7- updated all drivers.

Well, I also ran the Prime95 seft-test and this time, it showed a fatal error and pointed to hardware failure. Could this mean that my CPU is the culprit? I am attaching my minidumps and drwatson files. Any help would be appreciated.